The present invention relates to an instant film pack for containing a stack of integral or mono-sheet type instant film units.
As is well known in the instant photographic art, in integral or mono-sheet type diffusion transfer film units, an image-receiving sheet is assembled with a negative or photosensitive sheet in a single unit. The integral type instant film unit is provided, at one end, with a rupturable pod containing a developing reagent and at the opposite end with a trapping member for trapping and hardening excess developing reagent. A number of such integral type instant film units are stacked in a film pack.
This instant film pack is formed with an integral type instant film unit exit slot through which exposed film units are ejected one by one. For film safety, the film exit slot of the instant film pack is covered by a member opaque to light to block light entering into the instant film pack before the instant film pack is loaded in an instant camera. Used heretofore to prevent the integral type instant film units in the instant film pack from being exposed to ambient light or stray light is a light opaque member to cover over the film unit exit slot. In particular, a strip-like flexible light opaque member is attached to a top wall of the instant film pack along its one side and is releasably held by a thin plastic holding strip member heat-welded to a front wall of the instant film pack along its opposite side to cover a film unit exit slot formed in the front wall.
Such a light blocking member is broken by a protective cover sheet in the instant film pack which is ejected from the instant film pack and breaks the light blocking member to open the film unit exit slot. As is well known in the art, there is provided in the instant film pack a spring-supported pressure plate made of, for example, a thin steel sheet Which presses the stack of integral type instant film pack so as to place the foremost integral type instant film unit in the focal plane of the instant camera and to maintain it flat.
A problem associated with the manufacturing of such instant film packs is that at least two steps are required to apply the light blocking member to the instant film pack, namely a step to adhere one side of the light blocking member to the top wall of the instant film pack and a step to heat-weld the holding strip member to the front wall of the instant film pack so as to releasably hold the opposite side of the light blocking member. The necessity of such two steps increases the manufacturing cost of the instant film packs and decreases the manufacturing efficiency of the instant film packs.